real games vs. puzzles.

allow me to explain with a situation-

I am playing the chess tactics on this site.

I come to a puzzle where black moves his rook to h8. the H-file is open. blacks king is on h7 and once he moves to g8 he will get solid play down the H.

the problems rating is 1900s. after looking 5 minutes I guess a move and its wrong. the solution? the other rook was hanging.

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this is the kind of puzzle that you get instantly in a real game.on the flip side there are puzzles where theres a really hard mate but because you know a tactic is present you can find it, whereas a real game it would most likely slip away.

so the question is, (A)how can a player be strong when knowing/not knowing if there is a tactic, and (B) how to properly train tactics with this example in mind?